Topical Antiviral Formulations

ABSTRACT

The present invention relates to formulations of nucleotide reverse transcriptase inhibitors (N(t)RTIs), preferably [2-(6-Amino-purin-9-yl)-1-methyl-ethoxymethyl]-phosphonic acid (tenofovir, PMPA), or a physiologically functional derivative thereof, suitable for topical application and their use in the prevention of HIV infections.

FIELD OF THE INVENTION

The invention relates generally to formulations of compounds withantiviral activity and more specifically with anti-HIV properties.

BACKGROUND OF THE INVENTION

Human immunodeficiency virus (HIV) infection and related diseases are amajor public health problem worldwide. One approach to the problem ofHIV/AIDS is to reduce the risk of transmission of HIV and thus reducethe number of individuals who become newly infected. Even whentreatments or cures become available, prevention of infections in theinitial instance will likely remain as the first line of defense. Formedical, psychological, and economic reasons, it is preferable toprevent the initial infection, rather than treating, individuals withAIDS.

Education in regard to sexually transmitted diseases (STDs), their modesof transmission, and so-called “safe-sex” techniques has shown somepromise in reducing the risks of STD transmission through sexualactivity. Screening of the blood supply has helped to reduce the risk oftransmission of STD-causing organisms via blood transfusions and relatedmedical practices. Even with their known effectiveness in preventingSTDs, current safe-sex techniques are not always used, or are not alwaysused properly, for many reasons (e.g. carelessness, lack of knowledge,improper techniques, cultural barriers, unplanned or spontaneous sexualactivity, and the like). Moreover, even when used, safe-sex techniques(except perhaps abstinence) are not always effective.

Various commercial vaginal creams and ointments are currently available.Nonoxynol-9, octoxynol-9, and benzalkonium chloride are generallyavailable as suppositories, inserts, creams, films, foams, and gels.Examples of such commercial products include, for example, K-Y Plus™.(2.2 percent nonoxynol-9; Advanced Care Products, Raritan, N.J.);Encare™. (3 percent nonoxynol-9; Thompson Medical Co., West Palm Beach,Fla.); Gynol II (Advanced Care Products, Raritan, N.J.); Ortho OptionsConceptrol (Advanced Care Products, Raritan, N.J.); Semicid (WhitehallRobbins Healthcare, Madison, N.J.); and Advantage-S (ColumbiaLaboratories, Aventura, Fla.).

However, there is no formulation that is totally effective against HIV.It is desirable, therefore, to provide improved compositions and methodswhich reduce the risk of HIV transmission and/or infections duringsexual activity.

SUMMARY OF THE INVENTION

The present invention relates to formulations of nucleotide reversetranscriptase inhibitors (NRTIs), preferably[2-(6-Amino-purin-9-yl)-1-methyl-ethoxymethyl]-phosphonic acid(tenofovir, PMPA), or a physiologically functional derivative thereof,suitable for topical (e.g. vaginal, rectal, etc.) application and theiruse in the prevention of HIV infections.

This invention generally relates to compositions and methods whichprevent and/or reduce the risk of transmission of HIV through sexualactivity. Although it is mainly directed at heterosexual conduct (i.e.,male/female vaginal intercourse), the compositions of this invention mayalso be used by parties engaged in other types of sexual conduct. Forexample, the compositions of this invention could be used by partiesengaged in anal intercourse (male/female or male/male); compositions ofthis invention intended to be used in anal intercourse are preferablymodified to adjust the buffering capacity to pH values normally found inthe rectum and by altering the lubricity of the formulation.

For vaginal heterosexual intercourse, the composition may be insertedinto the vagina prior to intercourse. For anal intercourse (heterosexualor homosexual), the composition may be inserted into the rectum prior tointercourse. For either vaginal or anal intercourse, the composition mayalso act as a lubricant. For added protection it is generally preferredthat the composition be applied-before intercourse or other sexualactivity and that, if appropriate, a condom be used. For even furtherprotection, the composition may be reapplied as soon as possible aftercompletion of the sexual activity.

If desired, flavorants, scents, fragrances, and colorants may beincorporated into the composition so long as they do not interfere withthe safety or efficacy of the composition. Indeed, incorporation of suchflavorants, scents, fragrances, and colorants into the compositions ofthis invention may increase the probability that the composition will beused during sexual activity.

One advantage of the present method is that it can be used forprotection during a wide variety of sexual activities (vaginal or anal)by heterosexuals, bisexuals, and homosexuals. Another advantage of thepresent method of reducing the transmission of HIV is that this methodmay be implemented and/or used most easily by the party beingpenetrated. Thus, a woman may use the present method to protect herself(as well as her partner) with or without the partner's knowledge of themethod being used. Moreover, the partner would not be required to relyon his or her partner's claim of being AIDS-free or agreement to usecondoms for protection. Either or both sexual parties (especially thefemale participant) could initiate and implement the use of the presentmethod. Preferably the method is used before the sexual activity andmost preferably both before and after the sexual activity. Moreover, thecompositions of this invention offer the added benefit that they arealso useful in the prevention and/or treatment of bacterial vaginosis.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to certain embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with theenumerated embodiments, it will be understood that they are not intendedto limit the invention to those embodiments. On the contrary, theinvention is intended to cover all alternatives, modifications, andequivalents, which may be included within the scope of the presentinvention as defined by the claims.

DEFINITIONS

Unless stated otherwise, the following terms and phrases as used hereinare intended to have the following meanings:

The term “physiologically functional derivative” means apharmaceutically active compound with equivalent or near equivalentphysiological functionality to a given NRTI. As used herein, the term“physiologically functional derivative” includes any: physiologicallyacceptable salt, ether, ester, prodrug, solvate, stereoisomer includingenantiomer, diastereomer or stereoisomerically enriched or racemicmixture, and any other compound which upon administration to therecipient, is capable of providing (directly or indirectly) such acompound or an antivirally active metabolite or residue thereof.

“Bioavailability” is the degree to which the pharmaceutically activeagent becomes available to the target tissue after the agent'sintroduction into the body. Enhancement of the bioavailability of apharmaceutically active agent can provide a more efficient and effectivetreatment for patients because, for a given dose, more of thepharmaceutically active agent will be available at the targeted tissuesites.

The compounds of the combinations of the invention may be referred to as“active ingredients” or “pharmaceutically active agents.”

The term “prodrug” as used herein refers to any compound that whenadministered to a biological system generates the drug substance, i.e.active ingredient, as a result of spontaneous chemical reaction(s),enzyme catalyzed chemical reaction(s), and/or metabolic chemicalreaction(s).

“Prodrug moiety” means a labile functional group which separates fromthe active inhibitory compound during metabolism, systemically, inside acell, by hydrolysis, enzymatic cleavage, or by some other process(Bundgaard, Hans, “Design and Application of Prodrugs” in Textbook ofDrug Design and Development (1991), P. Krogsgaard-Larsen and H.Bundgaard, Eds. Harwood Academic Publishers, pp. 113-191). Prodrugmoieties can serve to enhance solubility, absorption and lipophilicityto optimize drug delivery, bioavailability and efficacy. A “prodrug” isthus a covalently modified analog of a therapeutically-active compound.

“Alkyl” means a saturated or unsaturated, branched, straight-chain,branched, or cyclic hydrocarbon radical derived by the removal of onehydrogen atom from a single carbon atom of a parent alkane, alkene, oralkyne. Typical alkyl groups consist of 1-18 saturated and/orunsaturated carbons, such as normal, secondary, tertiary or cycliccarbon atoms. Examples include, but are not limited to: methyl,Me(-CH₃), ethyl, Et(-CH₂CH₃), acetylenic(-C≡CH), ethylene,vinyl(-CH═CH₂), 1-propyl, n-Pr, n-propyl(-CH₂CH₂CH₃), 2-propyl, i-Pr,i-propyl(-CH(CH₃)₂), allyl(-CH₂CH═CH₂), propargyl(-CH₂C≡CH),cyclopropyl(-C₃H₅), 1-butyl, n-Bu, n-butyl(-CH₂CH₂CH₂CH₃),2-methyl-1-propyl, i-Bu, i-butyl(-CH₂CH(CH₃)₂), 2-butyl, s-Bu,s-butyl(-CH(CH₃)CH₂CH₃), 2-methyl-2-propyl, t-Bu, t-butyl(-C(CH₃)₃),1-pentyl, n-pentyl, (—CH₂CH₂CH₂CH₂CH₃), 2-pentyl(-CH(CH₃)CH₂CH₂CH₃),3-pentyl(-CH(CH₂CH₃)₂), 2-methyl-2-butyl(-C(CH₃)₂CH₂CH₃),cyclopentyl(-C₅H₉), 3-methyl-2-butyl(-CH(CH₃)CH(CH₃)₂),3-methyl-1-butyl(-CH₂CH₂CH(CH₃)₂), 2-methyl-1-butyl(-CH₂CH(CH₃)CH₂CH₃),1-hexyl(-CH₂CH₂CH₂CH₂CH₂CH₃),5-hexenyl(-CH₂CH₂CH₂CH₂CH≡CH₂)1-hexyl(-CH(CH₃)CH₂CH₂CH₂CH₃),3-hexyl(-CH(CH₂CH₃)(CH₂CH₂CH₃)), cyclohexyl(-C₆H₁₁),2-methyl-2-pentyl(-C(CH₃)₂CH₂CH₂CH₃),3-methyl-2-pentyl(-CH(CH₃)CH(CH₃)CH₂CH₃),4-methyl-2-pentyl(-CH(CH₃)CH₂CH(CH₃)₂),3-methyl-3-pentyl(-C(CH₃)(CH₂CH₃)₂),2-methyl-3-pentyl(-CH(CH₂CH₃)CH(CH₃)₂),2,3-dimethyl-2-butyl(-C(CH₃)₂CH(CH₃)₂), and3,3-dimethyl-2-butyl(-CH(CH₃)C(CH₃)₃.

“Aryl” means a monovalent aromatic hydrocarbon radical of 6-20 carbonatoms derived by the removal of one hydrogen atom from a single carbonatom of a parent aromatic ring system. Typical aryl groups include, butare not limited to, radicals derived from benzene, substituted benzene,naphthalene, anthracene, biphenyl, and the like.

“Arylalkyl:” refers to an acyclic alkyl radical in which one of thehydrogen atoms bonded to a carbon atom, typically a terminal or sp³carbon atom, is replaced with an aryl radical. Typical arylalkyl groupsinclude, but are not limited to, benzyl, 2-phenylethan-1-yl,2-phenylethen-1-yl, naphthylmethyl, 2-naphthylethan-1-yl,2-naphthylethen-1-yl, naphthobenzyl, 2-naphthophenylethan-1-yl and thelike. The arylalkyl group 6 to 20 carbon atoms e.g., the alkyl moiety,including alkanyl, alkenyl or alkynyl groups, of the arylalkyl group is1 to 6 carbon atoms and the aryl moiety is 5 to 14 carbon atoms.

“Substituted alkyl”, “substituted aryl”, and “substituted arylalkyl”mean alkyl, aryl, and arylalkyl respectively, in which one or morehydrogen atoms are each independently replaced with a substituent.Typical substituents include, but are not limited to, —X, —R, —O⁻, —OR,—SR, —S—, —NR₂, —NR₃, ═NR, —CX₃, —CN, —OCN, —SCN, —N═C═O, —NCS, —NO,—NO₂, ═N₂, —N₃, NC(═O)R, —C(═O)R, —C(═O)NRR—S(═O)₂O⁻, —S(═O)₂OH,—S(═O)₂R, —OS(═O)₂OR, —S(═O)₂NR, —S(═O)R,—OP(═O)O₂RR—P(═O)O₂RR—P(═O)(O⁻)₂, —P(═O)(OH)₂, —C(═O)R, —C(═O)X, —C(S)R,—C(O)OR, —C(O)O⁻, —C(S)OR, —C(O)SR, —C(S)SR, —C(O)NRR, —C(S)NRR,—C(NR)NRR, where each X is independently a halogen: F, Cl, Br, or I; andeach R is independently —H, alkyl, aryl, heterocycle, or prodrug moiety.

“Heteroaryl” and “Heterocycle” refer to a ring system in which one ormore ring atoms is a heteroatom, e.g. nitrogen, oxygen, and sulfur (asopposed to carbon). Heterocycles are described in: Katritzky, Alan R.,Rees, C. W., and Scriven, E. Comprehensive Heterocyclic Chemistry (1996)Pergamon Press; Paquette, Leo A.; Principles of Modern HeterocyclicChemistry W. A. Benjamin, New York, (1968), particularly Chapters 1, 3,4, 6, 7, and 9; “The Chemistry of Heterocyclic Compounds, A series ofMonographs” (John Wiley & Sons, New York, 1950 to present), inparticular Volumes 13, 14, 16, 19, and 28. Exemplary heterocyclesinclude but are not limited to pyrrole, indole, furan, benzofuran,thiophene, benzothiophene, 2-pyridyl, 3-pyridyl, 4-pyridyl, 2-quinolyl,3-quinolyl, 4-quinolyl, 2-imidazole, 4-imidazole, 3-pyrazole,4-pyrazole, pyridazine, pyrimidine, pyrazine, purine, cinnoline,pthalazine, quinazoline, quinoxaline, 3-(1,2,4-N)-triazolyl,5-(1,2,4-N)-triazolyl, 5-tetrazolyl, 4-(1-O, 3-N)-oxazole, 5-(1-O,3-N)-oxazole, 4-(1-S, 3-N)-thiazole, 5-(1-S, 3-N)-thiazole,2-benzoxazole, 2-benzothiazole, 4-(1,2,3-N)-benzotriazole, andbenzimidazole.

Stereochemical definitions and conventions used herein generally followS. P. Parker, Ed., McGraw-Hill Dictionary of Chemical Terms (1984)McGraw-Hill Book Company, New York; and Eliel, E. and Wilen, S.,Stereochemistry of Organic Compounds (1994) John Wiley & Sons, Inc., NewYork. Many organic compounds exist in optically active forms, i.e., theyhave the ability to rotate the plane of plane-polarized light. Indescribing an optically active compound, the prefixes D and L or R and Sare used to denote the absolute configuration of the molecule about itschiral center(s). The prefixes d and l or (+) and (−) are employed todesignate the sign of rotation of plane-polarized light by the compound,with (−) or 1 meaning that the compound is levorotatory. A compoundprefixed with (+) or d is dextrorotatory. For a given chemicalstructure, these compounds, called stereoisomers, are identical exceptthat they are mirror images of one another. A specific stereoisomer mayalso be referred to as an enantiomer, and a mixture of such isomers isoften called an enantiomeric mixture. A 50:50 mixture of enantiomers isreferred to as a racemic mixture or a racemate. The terms “racemicmixture” and “racemate” refer to an equimolar mixture of twoenantiomeric species, devoid of optical activity.

The term “chiral” refers to molecules which have the property ofnon-superimposability of the mirror image partner, while the term“achiral” refers to molecules which are superimposable on their mirrorimage partner.

The term “stereoisomers” refers to compounds which have identicalchemical constitution, but differ with regard to the arrangement of theatoms or groups in space.

“Diastereomer” refers to a stereoisomer with two or more centers ofchirality and whose molecules are not mirror images of one another.Diastereomers have different physical properties, e.g. melting points,boiling points, spectral properties, and reactivities. Mixtures ofdiastereomers may separate under high resolution analytical proceduressuch as electrophoresis and chromatography.

“Enantiomers” refer to two stereoisomers of a compound which arenon-superimposable mirror images of one another.

“Nucleoside and Nucleotide Reverse Transcriptase Inhibitors” or “NRTIs”include those compounds that exhibit anti-HIV effects by inhibiting theactivity of HIV reverse transcriptase. Examples include, but are notlimited to, abacavir (ABC), didanosine (ddI), emtricitabine (FTC),lamivudine (3TC), stavudine (d4T), tenofovir (TFV), zidovudine (AZT) andzalcitabine (ddC), and their physiologically functional derivatives. Oneor more NRTIs may be used in a formulation of this invention.

“Topical” formulations include those suitable for nasal, oral, rectal,transdermal, and vaginal administration.

PMPA or tenofovir (U.S. Pat. Nos. 4,808,716, 5,733,788, 6,057,305) hasthe structure:

The chemical names of PMPA, tenofovir include:(R)-9-(2-phosphonylmethoxypropyl)adenine; and phosphonic acid,[[(1R)-2-(6-amino-9H-purin-9-yl)-1-methylethoxy]methyl]. The CASRegistry number is 147127-20-6.

Tenofovir disoproxil fumarate (DF) is a nucleotide reverse transcriptaseinhibitor approved in the United States for the treatment of HIV-1infection in combination with other antiretroviral agents. Tenofovirdisoproxil fumarate or Viread® (Gilead Science, Inc.) is the fumaratesalt of tenofovir disoproxil. Viread® may be named as:2,4,6,8-Tetraoxa-5-phosphanonanedioic acid,5-[[(1R)-2-(6-amino-9H-purin-9-yl)-1-methylethoxy]methyl]-,bis(1-methylethyl)ester, 5-oxide, (2E)-2-butenedioate (1:1). The CASRegistry number is 202138-50-9.

Physiologically functional derivatives of tenofovir include thecompounds PMEA and PMPA. PMEA and PMPA have the structures:

where PMEA (R³ is H) and PMPA (R³ is C₁-C₆ alkyl, C₁-C₆ substitutedalkyl, or CH₂OR⁸ where R⁸ is C₁-C₆ alkyl, C₁-C₆ hydroxyalkyl or C₁-C₆haloalkyl. R⁶ and R⁷ are independently H or C₁-C₆ alkyl. R⁴and R⁵ areindependently H, NH₂, NHR or NR₂where R is C₁-C₆ alkyl. R¹ and R² areindependently H, C₁-C₆ alkyl, C₁-C₆ substituted alkyl, C₆-C₂₀ aryl,C₆-C₂₀ substituted aryl, C₆-C₂₀ arylalkyl, C₆-C₂₀ substituted arylalkyl,acyloxymethyl esters —CH₂OC(═O)R⁹ (e.g. POM) or acyloxymethyl carbonates—CH₂OC(═O)OR⁹ (e.g. POC) where R⁹ is C₁-C₆ alkyl, C₁-C₆ substitutedalkyl, C₆-C₂₀ aryl or C₆-C₂₀ substituted aryl. For example, R¹ and R²may be pivaloyloxymethoxy, POM, —CH₂OC(═O)C(CH₃)₃ or POC,—CH₂OC(═O)OC(CH₃)₃. Also for example, tenofovir has the structure whereR³ is CH₃, and R¹, R², R⁴, R⁵, R⁶ and R⁷ are H. Dialkyl phosphonates maybe prepared according to the methods of: Quast et. al. (1974) Synthesis490; Stowell et. al. (1990) Tetrahedron Lett. 3261; U.S. Pat. No.5,663,159.

PMPA may be enantiomerically-enriched or purified (single stereoisomer)where the carbon atom bearing R³ may be the R or S enantiomer. PMPA maybe a racemate, i.e. a mixture of R and S stereoisomers.

The invention includes all enantiomers, diastereomers, racemates, andenriched stereoisomer mixtures of PMPA, and physiologically functionalderivatives thereof.

The invention includes all prodrugs of tenofovir. A large number ofstructurally-diverse prodrugs have been described for phosphonic acids(Freeman and Ross in Progress in Medicinal Chemistry 34: 112-147 (1997).A commonly used prodrug class is the acyloxyalkyl ester, which was firstused as a prodrug strategy for carboxylic acids and then applied tophosphates and phosphonates by Farquhar et. al. (1983) J. Pharm. Sci.72: 324; also U.S. Pat. Nos. 4,816,570, 4,968,788, 5,663,159 and5,792,756. Subsequently, the acyloxyalkyl ester was used to deliverphosphonic acids across cell membranes and to enhance oralbioavailability. A close variant of the acyloxyalkyl ester strategy, thealkoxycarbonyloxyalkyl ester, may also enhance oral bioavailability as aprodrug moiety in the compounds of the combinations of the invention.Aryl esters of phosphorus groups, especially phenyl esters, are reportedto enhance oral bioavailability (DeLambert et. al. (1994) J. Med. Chem.37: 498). Phenyl esters containing a carboxylic ester ortho to thephosphate have also been described (Khamnei and Torrence, (1996) J. Med.Chem. 39:4109-4115). Benzyl esters are reported to generate the parentphosphonic acid. In some cases, substituents at the ortho-orpara-position may accelerate the hydrolysis. Benzyl analogs with anacylated phenol or an alkylated phenol may generate the phenoliccompound through the action of enzymes, e.g. esterases, oxidases, etc.,which in turn undergoes cleavage at the benzylic C—O bond to generatethe phosphoric acid and the quinone methide intermediate. Examples ofthis class of prodrugs are described by Mitchell et. al. (1992) J. Chem.Soc. Perkin Trans. I 2345; Brook et. al., WO 91/19721. Still otherbenzylic prodrugs have been described containing a carboxylicester-containing group attached to the benzylic methylene (Glazier et.al., WO 91/19721). Thio-containing prodrugs are reported to be usefulfor the intracellular delivery of phosphonate drugs. These proesterscontain an ethylthio group in which the thiol group is either esterifiedwith an acyl group or combined with another thiol group to form adisulfide. Deesterification or reduction of the disulfide generates thefree thio intermediate which subsequently breaks down to the phosphoricacid and episulfide (Puech et. al. (1993) Antiviral Res., 22: 155-174;Benzaria et. al. (1996) J. Med. Chem. 39: 4958). Cyclic phosphonateesters have also been described as prodrugs of phosphorus-containingcompounds.

Prodrug esters in accordance with the invention are independentlyselected from the following groups: (1) mono-, di-, and tri-phosphateesters of tenofovir or any other compound which upon administration to ahuman subject is capable of providing (directly or indirectly) saidmono-, di, or triphosphate ester; (2) carboxylic acid esters (3)sulphonate esters, such as alkyl- or aralkylsulphonyl (for example,methanesulphonyl); (4) amino acid esters (for example, alanine, L-valylor L-isoleucyl); (5) phosphonate; and (6) phosphonamidate esters. Estergroups (1)-(6) may be substituted with; straight or branched chainC₁-C₁₈ alkyl (for example, methyl, n-propyl, t-butyl, or n-butyl);C₃-C₁₂ cycloalkyl; alkoxyalkyl (for example, methoxymethyl); arylalkyl(for example, benzyl); aryloxyalkyl (for example, phenoxymethyl); C₅-C₂₀aryl (for example, phenyl optionally substituted by, for example,halogen, C₁-C₄ alkyl, or C₁-C₄ alkoxy); or amino. An exemplary arylmoiety present in such esters comprises a phenyl or substituted phenylgroup. Many phosphate prodrug moieties are described in U.S. Pat. No.6,312,662; Jones et. al. (1995) Antiviral Research 27:1-17; Kucera et.al. (1990) AIDS Res. Hum. Retro Viruses 6:491-501; Piantadosi et. al.(1991) J. Med. Chem. 34:1408-14; Hosteller et. al. (1992) Antimicrob.Agents Chemother. 36:2025-29; Hostetler et. al. (1990) J. Biol. Chem.265:611127; and Siddiqui et. al. (1999) J. Med. Chem. 42:4122-28.

Pharmaceutically acceptable prodrugs refer to a compound that ismetabolized in the host, for example hydrolyzed or oxidized, by eitherenzymatic action or by general acid or base solvolysis, to form anactive ingredient. Typical examples of prodrugs of the activeingredients of the combinations of the invention have biologicallylabile protecting groups on a functional moiety of the active compound.Prodrugs include compounds that can be oxidized, reduced, aminated,deaminated, esterified, deesterified, alkylated, dealkylated, acylated,deacylated, phosphorylated, dephosphorylated, or other functional groupchange or conversion involving forming or breaking chemical bonds on theprodrug.

Any reference to any of the above compounds also includes a reference toa physiologically acceptable salt thereof. Examples of physiologicallyacceptable salts of tenofovir and is physiologically acceptablederivatives include salts derived from an appropriate base, such as analkali metal (for example, sodium), an alkaline earth (for example,magnesium), ammonium and NX₄ ⁺ (wherein X is C₁-C₄ alkyl).Physiologically acceptable salts of an hydrogen atom or an amino groupinclude salts of organic carboxylic acids such as acetic, benzoic,lactic, fumaric, tartaric, maleic, malonic, malic, isethionic,lactobionic and succinic acids; organic sulfonic acids, such asmethanesulfonic, ethanesulfonic, benzenesulfonic and p-toluenesulfonicacids; and inorganic acids, such as hydrochloric, sulfuric, phosphoricand sulfamic acids. Physiologically acceptable salts of a compound of anhydroxy group include the anion of said compound in combination with asuitable cation such as Na⁺ and NX₄ ⁺ (wherein X is independentlyselected from H or a C₁-C₄ alkyl group).

For therapeutic use, salts of active ingredients of the invention willbe physiologically acceptable, i.e. they will be salts derived from aphysiologically acceptable acid or base. However, salts of acids orbases which are not physiologically acceptable may also find use, forexample, in the preparation or purification of a physiologicallyacceptable compound. All salts, whether or not derived form aphysiologically acceptable acid or base, are within the scope of thepresent invention.

Formulations include those suitable for nasal, oral, rectal,transdermal, and vaginal administration.

Formulations suitable for topical administration in the mouth includelozenges comprising the active ingredient in a flavored base, usuallysucrose and acacia or tragacanth; pastilles comprising the activeingredient in an inert basis such as gelatin and glycerin, or sucroseand acacia; and mouthwashes comprising the active ingredient in asuitable liquid carrier. Formulations for rectal administration may bepresented as a suppository with a suitable base comprising, for example,cocoa butter. Formulations suitable for vaginal administration may bepresented as tablets, pessaries, tampons, creams, gels, pastes, foams orspray formulations containing in addition to the active ingredient suchcarriers as are known in the art to be appropriate.

Pharmaceutical formulations suitable for rectal administration whereinthe carrier is a solid are most preferably presented as unit dosesuppositories. Suitable carriers include cocoa butter and othermaterials commonly used in the art. The suppositories may beconveniently formed by admixture of the active ingredient with thesoftened or melted carrier(s) followed by chilling and shaping inmoulds.

In the context of the present invention, it is to be understood that theterm topical application includes application to the body cavities aswell as to the skin. Thus, in a preferred embodiment, the NRTI isapplied to a body cavity such as the anus, the mouth, or the vagina. Ina particularly preferred embodiment, the NRTI is applied to the vagina.Thus, the present method may involve topical application to the vaginato prevent HIV infection as a result of vaginal intercourse. Typically,the topical application is carried out prior to the beginning of vaginalintercourse, suitably 0 to 60 minutes, preferably 0 to 5 minutes, priorto the beginning of vaginal intercourse.

The NRTI may be applied to the vagina in a number of forms includingaerosols, foams, jellies, creams, suppositories, tablets, tampons, etc.Compositions suitable for application to the vagina are disclosed inU.S. Pat. Nos. 2,149,240, 2,330,846, 2,436,184, 2,467,884, 2,541,103,2,623,839, 2,623,841, 3,062,715, 3,067,743, 3,108,043, 3,174,900,3,244,589, 4,093,730, 4,187,286, 4,283,325, 4,321,277, 4,368,186,4,371,518, 4,389,330, 4,415,585, and 4,551,148, which are incorporatedherein by reference, and the present method may be carried out byapplying the NRTI to the vagina in the form of such a composition. Thecomposition containing the NRTI may be applied to the vagina in anyconventional manner. Suitable devices for applying the composition tothe vagina are disclosed in U.S. Pat. Nos. 3,826,828, 4,108,309,4,360,013, and 4,589,880, which are incorporated herein by reference.

In another embodiment, the present invention involves topicaladministration of the NRTI to the anus. The composition administered tothe anus is suitably a foam, cream, jelly, etc., such as those describedabove with regard to vaginal application. In the case of analapplication, it may be preferred to use an applicator which distributesthe composition substantially evenly throughout the anus. For example, asuitable applicator is a tube 2.5 to 25 cm, preferably 5 to 10 cm, inlength having holes distributed regularly along its length.

In another embodiment, the present method may be carried out by applyingthe NRTI orally. Oral application is suitably carried out by applying acomposition which is in the form of a mouthwash or gargle. Oralapplication is especially preferred to prevent infection during dentalprocedures. Suitably, the composition is applied just prior to thebeginning of the dental procedure and periodically throughout theprocedure.

The present invention also provides compositions useful for preventingthe spread of HIV infection. As noted above, such compositions may be inthe form of foams, creams, jellies, suppositories, tablets, aerosols,gargles, mouthwashes, etc. Particularly preferred are vaginal gels. Theconcentration of NRTI in the composition is such to achieve an effectivelocal anal, oral or vaginal concentration upon administration of theusual amount of the type of composition being applied. In this regard,it is noted that when the composition is in the form of a suppository(including vaginal suppositories), the suppository will usually be 1 to5 grams, preferably about 3 grams, and the entire suppository will beapplied. A vaginal tablet will suitably be 1 to 5 grams, preferablyabout 2 grams, and the entire tablet will be applied. When thecomposition is vaginal cream, suitably 0.1 to 2 grams, preferably about0.5 grams of the cream will be applied. When the composition is awater-soluble vaginal cream, suitably 0.1 to 2 grams, preferably about0.6 grams, are applied. When the composition is a vaginal spray-foam,suitably 0.1 to 2 grams, preferably about 0.5 grams, of the spray-foamare applied. When the composition is an anal cream, suitably 0.1 to 2grams, preferably about 0.5 grams of the cream is applied. When thecomposition is an anal spray-foam, suitably 0.1 to 2 grams, preferablyabout 0.5 grams of the spray-foam are applied. When the composition is amouthwash or gargle, suitably 1 to 10 ml, preferably about 5 ml areapplied.

In the case of a mouthwash or gargle, it may be preferred to include inthe composition an agent which will mask the taste and/or odor of theNRTI. Such agents include those flavoring agents typically found inmouthwashes and gargles, such as spearmint oil, cinnamon oil, etc.

The present compositions may also be in the form of a time-releasecomposition. In this embodiment, the NRTI is incorporated in acomposition which will release the active ingredient at a rate whichwill result in an effective vaginal or anal concentration of NRTI.Time-release compositions are disclosed in Controlled Release ofPesticides and Pharmaceuticals, D. H. Lew, Ed., Plenum Press, New York,1981; and U.S. Pat. Nos. 5,185,155; 5,248,700; 4,011,312; 3,887,699;5,143,731; 3,640,741; 4,895,724; 4,795,642; Bodmeier et. al., Journal ofPharmaceutical Sciences, vol. 78 (1989); Amies, Journal of Pathology andBacteriology, vol. 77 (1959); and Pfister et. al., Journal of ControlledRelease, vol. 3, pp. 229-233 (1986), all of which are incorporatedherein by reference.

The present compositions may also be in the form which releases the NRTIin response to some event such as vaginal or anal intercourse. Forexample, the composition may contain the NRTI in vesicles or liposomes,which are disrupted by the mechanical action of intercourse.Compositions comprising liposomes are described in U.S. Pat. No.5,231,112 and Deamer and Uster, “Liposome Preparation: Methods andMechanisms”, in Liposomes, pp. 27-51 (1983); Sessa et. al., J. Biol.Chem., vol. 245, pp. 3295-3300 (1970); Journal of Pharmaceutics andPharmacology, vol. 34, pp. 473-474 (1982); and Topics in PharmaceuticalSciences, D. D. Breimer and P. Speiser, Eds., Elsevier, New York, pp.345-358 (1985), which are incorporated herein by reference.

It should also be realized that the present compositions may beassociated with an article, such as an intrauterine device (IUD),vaginal diaphragm, vaginal sponge, pessary condom, etc. In the case ofan IUD or diaphragm, time-release and/or mechanical-release compositionsmay be preferred, while in the case of condoms, mechanical-releasecompositions are preferred.

In another embodiment, the present invention provides novel articles,which are useful for the prevention of HIV infection. In particular, thepresent articles are those which release the NRTI when placed on anappropriate body part or in an appropriate body cavity. Thus, thepresent invention provides IUDs, vaginal diaphragms, vaginal sponges,pessaries, or condoms which contain or are associated with an NRTI.

Thus, the present article may be an IUD which contains one or moreNRTIs. Suitable IUDs are disclosed in U.S. Pat. Nos. 3,888,975 and4,283,325 which are incorporated herein by reference. The presentarticle may be an intravaginal sponge which comprises and releases, in atime-controlled fashion, the NRTI. Intravaginal sponges are disclosed inU.S. Pat. Nos. 3,916,898 and 4,360,013, which are incorporated herein byreference. The present article may also be a vaginal dispenser, whichreleases the NRTI. Vaginal dispensers are disclosed in U.S. Pat. No.4,961,931, which is incorporated herein by reference.

The present article may also be a condom which is coated with an NRTI.In a preferred embodiment, the condom is coated with a lubricant orpenetration enhancing agent which comprises an NRTI. Lubricants andpenetration enhancing agents are described in U.S. Pat. Nos. 4,537,776;4,552,872; 4,557,934; 4,130,667, 3,989,816; 4,017,641; 4,954,487;5,208,031; and 4,499,154, which are incorporated herein by reference.

EXAMPLES

The following examples further describe and demonstrate particularembodiments within the scope of the present invention. The examples aregiven solely for illustration and are not to be construed as limitationsas many variations are possible without departing from spirit and scopeof the Invention. The following examples are intended for illustrationonly and are not intended to limit the scope of the invention in anyway. “Active ingredient” denotes one or more NRTIs, as defined above,preferably tenofovir or a physiologically functional derivative thereof.

Formulation A (Controlled Release Formulation):

This formulation is prepared by wet granulation of the ingredients withpurified water, followed by the addition of magnesium stearate andcompression. The hypromellose can utilize varying viscosity grades.mg/tablet Active ingredient 300 Hypromellose 112 Lactose Monohydrate 53Pregelatinized Starch 28 Magnesium Stearate 7 Purified Water q.s.

Drug release takes place over a period of about 6-8 hours and iscomplete after 12 hours.

Formulation B (Controlled Release Capsule):

The following controlled release capsule formulation is manufactured bypreparing a wet granulation of ingredients a, b, c and e, and thenextruding the material using an extruder, followed by spheronization ofthe extrudate and drying. The dried pellets are then coated with arelease-controlling membrane (d) or polymer. The final product is filledinto a two-piece, hard gelatin or hydroxypropyl methylcellulose capsule.mg/capsule (a) Active Ingredient 300 (b) Microcrystalline Cellulose 125(c) Lactose Monohydrate 125 (d) Ethyl Cellulose  13 (e) Purified Waterq.s. (f) Gelatin capsules

Formulation C (Oral Suspension):

The active ingredients are admixed with the other ingredients and filledas dry powder. Purified water is added and mixed well before use. ActiveIngredient 300 mg Confectioner's Sugar 2000 mg  Simethicone 300 mgMethylparaben  30 mg Propylparaben  10 mg Flavor, Peach 500 mg PurifiedWater q.s. to 5.00 ml 

Formulation D (Suppository):

One-fifth of the Witepsol H15 is melted in a steam-jacketed pan at 45°C. maximum. The active ingredients are sifted through a 200 micron sieveand added to the molten base with mixing, using a Silverson fitted witha cutting head, until a smooth dispersion is achieved. Maintaining themixture at 45° C., the remaining Witepsol H15 is added to the suspensionand stirred to ensure a homogenous mix. The entire suspension is passedthrough a 250 micron stainless steel screen and, with continuousstirring, is allowed to cool to 40° C. At a temperature of 38° C. to 40°C., 2.02 g of the mixture is filled into suitable, 2 ml plastic molds.The suppositories are allowed to cool to room temperature.mg/Suppository Active Ingredient 300 Hard Fat, B.P. (Witepsol H15 -Dynamit Nobel) 1770

Formulation E (Vaginal Suppositories) Active ingredient 300 mgHexanetriol 100 mg Polyethylene glycol 1500 q.s.

Formulation F (Vaginal Cream) Active ingredient 300 mg Nonionicautoemulsifying base  4 g Water balance to 100 g 

Formulation G (Vaginal Spray-Foam) Active ingredient 300 mg Polyethyleneglycol 6000  2 g Nonionic emulsifying agent  2 g Water 85 g Freon 12/144(70:30) 10 g

Formulation H (Vaginal Gel) Tenofovir 1.00 (% w/w)Hydroxyethylcellulose, NF (Natrasol ®•250H) 2.50 Propylparaben, NF 0.02Methylparaben, NF 0.18 Edetate Disodium, USP 0.05 Glycerin, USP 20.00Citric Acid, USP 1.00 Purified Water, USP 75.25 Total 100.00

Sodium hydroxide and hydrochloric acid are used as 10% w/w solutions toadjust pH to a target of 4.4. The methylparaben and propylparaben aredissolved in heated glycerin. Hydroxyethylcellulose is added anddispersed to form an organic phase. Edetate disodium and citric acid aredissolved in purified water, tenofovir is added and dispersed, pHadjusted to 4.4, and solution clarified by passage through a 0.22 μmfilter. Aqueous and organic phases are mixed, stirred well then filledinto tubes or applicators.

Safety and Tolerability

Tenofovir vaginal gel used 1% BID was well-tolerated in abstinent andsexually active HIV(−) and HIV(+) women, with limited systemicabsorption and with possible beneficial effects on vaginal microflora.

All publications and patent applications cited herein are incorporatedby reference to the same extent as if each individual publication orpatent application was specifically and individually indicated to beincorporated by reference.

Although certain embodiments have been described in detail above, thosehaving ordinary skill in the art will clearly understand that manymodifications are possible in the embodiments without departing from theteachings thereof. All such modifications are intended to be encompassedwithin the claims of the invention.

1. A method for the prevention of the symptoms or effects of an HIVinfection in an infected animal which comprises administering to saidanimal a prophylactically effective amount of a topical formulationcomprising an effective amount of an NRTI in combination with apharmaceutically acceptable vehicle.
 2. A method according to claim 1wherein the NRTI comprises[2-(6-Amino-purin-9-yl)-1-methyl-ethoxymethyl]-phosphonic aciddiisopropoxycarbonyloxymethyl ester (tenofovir) or a physiologicallyfunctional derivative thereof.
 3. The method according to claim 2wherein the formulation comprises from about 0.2 to about 2 weightpercent tenofovir.
 4. The method according to claim 1 wherein the NRTIcomprises a physiologically functional derivative of tenofovir which hasthe structure:

wherein R¹ and R² are independently selected from H, C₁-C₆ alkyl, C₁-C₆substituted alkyl, C₆-C₂₀ aryl, C₆-C₂₀ substituted aryl, C₆-C₂₀arylalkyl, C₆-C₂₀ substituted arylalkyl, acyloxymethyl esters —CH₂OC═O)Rand acyloxymethyl carbonates —CH₂OC(═O)OR⁹ where R⁹ is C₁-C₆ alkyl,C₁-C₆ substituted alkyl, C₆-C₂₀ aryl or C₆-C₂₀ substituted aryl; R³ is HC₁-C₆ alkyl, C₁-C₆ substituted alkyl, or CH₂OR⁸ where R⁸ is C₁-C₆ alkyl,C₁-C₆ hydroxyalkyl or C₁-C₆ haloalkyl; R⁴ and R⁵ are independentlyselected from H, NH₂, NHR and NR₂ where R is C₁-C₆ alkyl; and R⁶ and R⁷are independently selected from H and C₁-C₆ alkyl.
 5. A pharmaceuticalformulation comprising an NRTI and a pharmaceutically acceptable mediumsuitable for topical application.
 6. A pharmaceutical formulationcomprising [2-(6-Amino-purin-9-yl)-1-methyl-ethoxymethyl]-phosphonicacid diisopropoxycarbonyloxymethyl ester (tenofovir) or aphysiologically functional derivative thereof and a pharmaceuticallyacceptable medium suitable for topical application.
 7. The formulationaccording to claim 5 wherein the NRTI comprises a physiologicallyfunctional derivative of tenofovir which has the structure:

wherein R¹ and R² are independently selected from H, C₁-C₆ alkyl, C₁-C₆substituted alkyl, C₆-C₂₀ aryl, C₆-C₂₀ substituted aryl, C₆-C₂₀arylalkyl, C₆-C₂₀ substituted arylalkyl, acyloxymethyl esters—CH₂OC(═O)R and acyloxymethyl carbonates —CH₂OC(═O)OR⁹ where R⁹ is C₁-C₆alkyl, C₁-C₆ substituted alkyl, C₆-C₂₀ aryl or C₆-C₂₀ substituted aryl;R³ is H, C₁-C₆ alkyl, C₁-C₆ substituted alkyl, or CH₂OR⁸ where R⁸ isC₁-C₆ alkyl, C₁-C₆ hydroxyalkyl or C₁-C₆ haloalkyl; R⁴ and R⁵ areindependently selected from H, NH₂, NHR and NR₂ where R is C₁-C₆ alkyl;and R⁶ and R⁷ are independently selected from H and C₁-C₆ alkyl.
 8. Agel formulation of claims 5 to
 7. 9. A cream formulation of claims 5 to7.
 10. A foam formulation of claims 5 to
 7. 11. A suppositoryformulation of claims 5 to
 7. 12. A condom coated with a formulation ofclaims 5 to 7.